Brief outline of the issue

lettrine-xetex-bidi.def patches an old definition of the internal command @lettrine of the lettrine package leading to issues with the current implementation.

Rather than updating the patched definition in lettrine-xetex-bidi.def, I suggest to include the RTL flag mechanism for the \parshape command in the original definition of @lettrine. I have an experimental version of lettrine.sty, appended here. Please let me know
lettrine.sty.gz
if something like that would enable to get rid of lettrine-xetex-bidi.def?

Check/indicate

• Relevant to the xepersian package
• [ x] The bidi package issue tracker has been searched for similar issues?
• The xepersian package issue tracker has been searched for similar issues?
• Links to <tex.stackexchange.com> discussion if appropriate
• Links to <qa.parsilatex.com> discussion if appropriate

Minimal example showing the issue

% !TEX TS-program = XeLaTeX
% !TEX encoding = UTF-8 Unicode


\documentclass{article}            % or some other class

  % Any packages other than the bidi package must be loaded here
\usepackage{lettrine}

  % The bidi package must be loaded as the last package
\usepackage{bidi}

  % Any preamble code goes here
  
\begin{document}

 \lettrine{V}{oici} un exemple 

\end{document}

Expected behavior

Log and PDF files

! Undefined control sequence.
\LettrineFont \L@initial